388 P WAVE AMPLITUDE CHANGES IN PATIENTS WITH NORMAL AND ABNORMAL EXERCISE TESTS. (1st January 2005) - Reimert, M.
Abstract : Purpose: To assess the relationship between exercise-induced myocardial ischemia and changes in atrial activity. Several investigators have postulated that inadequate ventricular output due to exercise-induced ischemia can lead to altered atrial contractility. These changes may be accompanied by measurable changes in P wave amplitude (Py) in patients with normal (N) and abnormal (+) exercise tests. Methods: Retrospective analysis of Py was conducted by selecting 87 consecutive patients who underwent exercise stress tests (EST) according to the Bruce protocol. All patients were required to reach 85% of their target heart rate for inclusion in this study. Baseline measurements of Py were recorded in the supine position in leads II, aVF, V1, V5 and V6 using a 5x magnifier. These measurements were repeated at maximum exercise in each lead. Subjects were then classified as having either a "+" (n=36) or "N" (n=48) EST based on changes in their ST segment morphology. Independent sample, one-tailed t-tests were then conducted to see if "+" patients had greater increases in Py percent change from supine to exercise than "N" patients. Three patients were eliminated from the final analysis due to missing values. Results: The mean Py exercise values were significantly greater than the supine values in all leads (p≤0.0001). The mean Py percent change from supine to maximum exercise was greater in patients with a "+" EST than in patients with a "N" EST (52.4% greater in V1, 52.5% in V5, 59.2% in V6, 6.7% in II, and 10.9% in aVF). This increase was statistically significant in leads V1, V5 and V6 (p=0.0479, 0.0197, and 0.0155 respectively), however, the mean difference between "+" and "N" patients in leads II and aVF was not significant (p= 0.3308 and 0.2843). Conclusions: Py typically increases in response to exercise. Patients with a "+" EST have greater increases in Py in leads V1, V5 and V6, than patients with a "N" EST. The atrial response to decreased left ventricular function associated with exercise-induced ischemia may be reflected in Py increases. Further assessment of P wave changes in response to exercise may add diagnostic and prognostic value to the EST.